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A lumped model of the dynamics of the controlled switching of high-Q closed-mode structures in rectangular large cavities (up to 1 × 1 mm and larger) based on AlGaAs/InGaAs/GaAs laser heterostructures is presented. The model considers the modulation of the useful power of a closed-mode structure due to controlled generation switching to an alternative closed mode. Generation-switching control between closed mode structures is implemented due to a variation in the optical loss of one structure. A variation in the optical loss occurs due to an increase in interband optical absorption due to the quantum-confined Stark effect upon the application of voltage to a laser crystal segment in the closed-mode propagation region.

This study is concerned with the specific features of how high-Q closed modes operating on the total-internal-reflection effect in large-size (up to hundreds or thousands of wavelengths) rectangular resonators based on InGaAs/GaAs/AlGaAs laser heterostructures are formed. The specific features of the spectral composition and spatial configurations of closed-mode configurations are experimentally examined. The presence of frequency combs in the spectra is demonstrated and their correspondence to the separate spatial configurations of closed modes is shown. The effect of changing the pumping level and the temperature on the mode composition of the emission is also considered.

Due to internal optical absorption loss, which varies with carrier density in the optical confinement region, the operating characteristics can be two valued in semiconductor quantum well lasers. Particularly, there can be two lasing thresholds and two branches in the light–current characteristic. While the internal differential quantum efficiency for the first (conventional) branch of the light–current characteristic is less than 1 and decreases with increasing pump current, that for the second (unconventional) branch is greater than 1 and nonmonotonous.

The light-current characteristic (LCC) of semiconductor quantum well lasers is theoretically studied. It is discussed here that, due to internal optical absorption loss, which depends on the electron and hole densities in the optical confinement layer, (i) roll-over of the LCC occurs with increasing injection current, and, (ii) depending on the parameters of laser structures, the LCC can have two branches, i.e. the optical emission at two different output powers will be possible within a certain range of injection currents.

The operating characteristics of semiconductor quantum-well lasers, calculated with consideration for an increase in the internal optical loss in the waveguide region with increasing pump current, are presented. The condition of global electroneutrality in the structure is used. This condition consists in that the total charge of electrons in the 2D active region (quantum well) and bulk waveguide region (optical confinement layer) is equal to the total charge of holes in these two regions. Good agreement between the calculated and experimentally determined light–current characteristics is obtained.

Pulse-pumped MOVPE-fabricated (metal-organic vapor-phase epitaxy) semiconductor lasers emitting in the spectral ranges 1000–1100 and 1400–1600 nm at temperatures of 110–120 K are studied. It is found that cooling the lasers for both spectral ranges to low temperature results in their light–current curves approaching linearity, and an optical power of, respectively, 110 and 20 W can be attained. The low-temperature effect is reduced for lasers emitting in the spectral range 1400–1600 nm. The processes affecting a rise in the internal optical loss in semiconductor lasers are considered. It is shown that an increase in the carrier concentration in the waveguide of a laser structure greatly depends on temperature and is determined by the noninstantaneous capture (capture rate) of carriers from the waveguide into the active region. It is demonstrated that, upon lowering the temperature to 115K, the concentration of electrons and holes in the waveguide becomes lower, which leads to a significant decrease in the internal optical loss and to an increase in the output optical power of the semiconductor laser.

Threshold characteristics of a semiconductor quantum-well (QW) laser are calculated using the global electroneutrality condition, which includes charge carriers both in the active and waveguide regions and thus presents an equality of the total charge of electrons to the total charge of holes in these two regions. It is shown that at the lasing threshold, the densities of electrons in the QW and the waveguide region are not equal to the densities of holes in these regions, i.e., the local electroneutrality condition is violated in each of the regions. Depending on the velocities of the carrier capture from the waveguide region into the QW, the electron density can be either higher or lower than the hole density (both in the QW and in the waveguide region). The charge of the carriers of each sign in the waveguide region is shown to be greater than that in the QW.

High-order surface diffraction gratings acting as a distributed Bragg reflector (DBR) in mesa stripe semiconductor lasers (λ = 1030 nm) have been studied theoretically and experimentally. Higher order interfering radiation modes (IRMs), which propagate off the plane of the waveguide, have been shown to have a crucial effect on the reflection and transmission spectra of the DBR. The decrease in the reflectivity of the DBR in response to the increase in the diffraction efficiency of these modes may reach 80% and more. According to theoretical analysis results, the intensity of the higher order IRMs is determined by the geometry of the DBR groove profile. Experimental data demonstrate that the noncavity modes are responsible for parasitic light leakage losses in the laser cavity. It has been shown that, in the case of nonoptimal geometry of the grating groove profile, the overall external differential quantum efficiency of the parasitic laser emission may exceed 45%, which is more than half of the laser output power. The optimal geometry of the DBR groove profile is trapezoidal, with the smallest possible lower base. Experimental evidence has been presented that this geometry considerably reduces the power of the higher order IRMs and minimises the parasitic light leakage loss.

Threshold and power characteristics of quantum well lasers are theoretically studied in the presence of internal optical absorption loss. Due to variation of the internal loss coefficient with electron and densities in the optical confinement layer of the laser, the light-current characteristic may have two branches, each with its own threshold. The branches merge together at the maximum operating current.

Free carrier absorption in heterostructure layers of an operating laser diode has been measured. The proposed technique is based on coupling pulse probe light emission into the laser waveguide. Lasers with various heterostructure designs were measured at different current and temperature levels up to 30 kA/cm2 and 85°C. The dependencies sufficiently describe the laser characteristics and can be used for heterostructure design comparison and optimization.

The operating characteristics of a semiconductor quantum-well laser calculated using three models are compared. These models are (i) a model not taking into account differences between the electron and hole parameters and using the electron parameters for both types of charge carriers; (ii) a model, which does not take into account differences between the electron and hole parameters and uses the hole parameters for both types of charge carriers; and (iii) a model taking into account the asymmetry between the electron and hole parameters. It is shown that, at the same velocity of electron and hole capture into an unoccupied quantum well, the laser characteristics, obtained using the three models, differ considerably. These differences are due to a difference between the filling of the electron and hole subbands in a quantum well. The electron subband is more occupied than the hole subband. As a result, at the same velocities of electron and hole capture into an empty quantum well, the effective electron-capture velocity is lower than the effective hole-capture velocity. Specifically, it is shown that for the laser structure studied the hole-capture velocity of 5 × 105 cm/s into an empty quantum well and the corresponding electron-capture velocity of 3 × 106 cm/s into an empty quantum well describe the rapid capture of these carriers, at which the light–current characteristic of the laser remains virtually linear up to high pump-current densities. However, an electron-capture velocity of 5 × 105 cm/s and a corresponding hole-capture velocity of 8.4 × 104 cm/s describe the slow capture of these carriers, causing significant sublinearity in the light–current characteristic.

We have studied the effect of laser cavity parameters on the light–current characteristics of lasers based on the AlGaInAs/GaInAsP/InP solid solution system that emit in the spectral range 1400 – 1600 nm. It has been shown that optimisation of cavity parameters (chip length and front facet reflectivity) allows one to improve heat removal from the laser, without changing other laser characteristics. An increase in the maximum output optical power of the laser by 0.5 W has been demonstrated due to cavity design optimisation.

We report an experimental study of power characteristics of semiconductor lasers based on MOVPE-grown asymmetric separate-confinement heterostructures with a broadened waveguide as functions of cavity length, stripe contact width and mirror reflectivities. It is shown that at high current pump levels, the variation of the cavity parameters of a semiconductor laser (width, length and mirror reflectivities) influences the light – current (L – I) characteristic saturation and maximum optical power by affecting such laser characteristics, as the current density and the optical output loss. A model is elaborated and an optical power of semiconductor lasers is calculated by taking into account the dependence of the internal optical loss on pump current density and concentration distribution of charge carriers and photons along the cavity axis of the cavity. It is found that only introduction of the dependence of the internal optical loss on pump current density to the calculation model provides a good agreement between experimental and calculated L – I characteristics for all scenarios of variations in the laser cavity parameters.

Semiconductor lasers based on MOVPE-grown asymmetric separate-confinement heterostructures with a broadened waveguide and emitting in the wavelength range 1.0 – 1.1 μm are studied. It is found that the intensity of spontaneous emission from the active region increases with increasing pump current above the lasing threshold and that this is caused by a growth in the concentration of charge carriers in the active region due to the modal gain enhancement needed to compensate for the growing internal optical loss at high pulsed pump currents. It is shown that the increase in the internal optical loss with increasing pulsed pump current is one of the main reasons for saturation of the light – current characteristics of high-power semiconductor lasers.

The effect of temperature delocalization in semiconductor lasers (emission wavelength λ = 1060 nm) based on symmetric and asymmetric separate-confinement heterostructures fabricated by metal-organic vapor-phase epitaxy (MOVPE) is studied. Experimental and calculated estimates show that the carrier concentration in the waveguide increases by an order of magnitude when the temperature of a semiconductor laser is raised by ∼100°C. It is found that an increase in the temperature of the active zone leads to enhancement of the temperature delocalization of both electrons and holes. It is shown that the delocalization of holes begins at higher temperatures, compared with that of electrons. It is demonstrated experimentally that the onset of temperature delocalization depends on the threshold carrier concentration in the active region of a laser at room temperature. It is found that raising the energy depth of the active region by choosing the waveguide material makes it possible to fully suppress the temperature-delocalization process up to 175°C.

Using an extended theoretical model, which includes the rate equations for both electrons and holes, we have studied the output characteristics of semiconductor quantum-well lasers. We have found non-trivial dependences of electron and hole concentrations in the waveguide region of the laser on the capture velocities of both types of carriers from the waveguide region into the quantum well. We have obtained the dependences of the internal differential quantum efficiency and optical output power of the laser on the capture velocities of electrons and holes. An increase in the capture velocities has been shown to result in suppression of parasitic recombination in the waveguide region and therefore in a substantial increase in the quantum efficiency and output power.

A method of studying the absorption coefficient in layers of semiconductor lasers is proposed. Using lasers based on MOVPE-grown separate-confinement heterostructures with a broadened waveguide, the absorption coefficient is investigated under pulsed current pumping. It is found that when the pump current flows through the laser in question, an additional internal optical absorption arises in the heterostructure layers. It is shown that an increase in the pump current density up to 20 kA cm-2 leads to an increase in absorption up to 2.5 cm-1. The feasibility of studying free-carrier absorption in the active region is demonstrated.

The process of charge carrier delocalization in high-power semiconductor lasers is examined under high current, pulse-pumped operation conditions. It is established that the carrier delocalization process is mostly determined by the injection of electrons (rather than holes) into the waveguide. Two methods of suppression of carrier delocalization are experimentally demonstrated, which are based on increasing the waveguide bandgap width and on using the waveguide containing a potential energy barrier for electrons in the p-region.

Laser diodes with a deep built-in trapezoidal large-period diffraction grating have been developed on the basis of InGaAs/GaAs/AlGaAs heterostructures. The electroluminescence and stimulated emission spectra and light-current characteristics of diffraction-grating laser diodes have been studied. A substantial narrowing of both the luminescence and stimulated emission spectra was achieved due to the spectral selectivity of the grating. The maximum output optical power was 1 W at a drive current of 4 A. At the highest power, the lasing spectrum had a FWHM of ∼2 A. A narrowing of the lasing spectrum of the diffraction-grating laser by tens of times was demonstrated, compared with that of a laser with a Fabry-Perot cavity.

The temperature dependences of the threshold current density and threshold concentration in semiconductor lasers based on MOVPE-grown asymmetric separate-confinement heterostructures with an extended waveguide have been studied (wavelengths λ = 1050–1070). It is shown that the temperature dependence of the threshold current density in semiconductor lasers becomes markedly stronger at above-room temperatures, which is due to temperature-induced carrier delocalization into the waveguide layers of a laser heterostructure. It was found that the sharp decrease in the thermal stability of the threshold current density with increasing temperature correlates with the coincidence of the Fermi level with the conduction-band bottom of the waveguide layer in the laser heterostructure. It is experimentally demonstrated that an increase in the energy depth and number of quantum wells in the active region of a semiconductor laser improves the thermal stability of the threshold current density. It is demonstrated that the characteristic parameter T0 attains a value of 220 K in the temperature range from −20 to +70°C.

The light-current characteristic of a semiconductor laser with multiple quantum wells (QWs) is calculated, with the delayed capture of charge carriers from the waveguide region into the wells taken into account. It is shown that increasing the number of QWs is a more effective way to improve the power characteristics of a laser, compared with an increase in the velocity of carrier capture into each of the wells. For example, using two QWs as the active region leads to a substantial increase in the internal quantum efficiency of stimulated emission and to a significantly better linearity of the light-current characteristic of the laser, compared with a single-well structure. At the same time, using three or more QWs only slightly improves the power characteristics of the laser, compared with the double-well structure. Thus, a double-well structure is the optimal as regards high output power and simplicity of growth.

A deep diffraction grating with a large period (∼2 μm) within one of the cladding layers is proposed for the implementation of selective feedback in a semiconductor laser. Frequency dependences of reflectance in the 12th diffraction order for rectangular, triangular, and trapezoidal diffraction gratings are calculated. It is shown that the maximum reflectance of the waveguide mode is attained using a rectangular or trapezoidal grating ∼2 μm deep in the laser structure. Deep trapezoidal diffraction gratings with large periods are fabricated in the Al0.3Ga0.7As cladding layer of a GaAs/AlGaAs laser structure using photolithography and reactive ion etching.

Threshold conditions for generation of a closed mode in the crystal of the Fabry-Perot semiconductor laser with a quantum-well active region are analyzed. It is found that main parameters affecting the closed mode lasing threshold for the chosen laser heterostructure are as follows: the optical loss in the passive region, the optical confinement factor of the closed mode in the gain region, and material gain detuning. The relations defining the threshold conditions for closed mode lasing in terms of optical and geometrical characteristics of the semiconductor laser are derived. It is shown that the threshold conditions can be satisfied at a lower material gain in comparison with the Fabry-Perot cavity mode due to zero output loss for the closed mode.

Advantages of the concept of high-powered semiconductor nanoheterostructure lasers for the spectral range 1700–1800 nm, grown by MOCVD in the InGaAsP/InP solid solution system, have been experimentally demonstrated. It has been found that using an expanded waveguide enables reduction to 2 cm−1 of the internal optical loss in quantum-well asymmetric separate-confinement double InGaAsP/InP heterostructures emitting at a wavelength of 1.76 µm. The heterostructures developed have been used to create multimode lasers with a room-temperature CW output power of 2.5 W in an aperture of 100 µm. It is shown that use of highly stressed quantum-well InGaAs layers as the active region makes it possible to obtain characteristic temperatures T0 = 50–60 K.

The possibility of using the normal skin effect in dielectric waveguides for long-wavelength radiation is analyzed. A design of a waveguide integrated with a heterolaser is suggested, in which an undoped layer of GaAs is clad between heavily-doped n- and p-AlxGa1 − x As alloy layers, reflecting radiation because of the normal skin effect. It is shown that an efficient waveguide can be formed using n-AlxGa1 − x As layers with x 5 × 1018 cm−3 and p-AlxGa1 − x As layers of any composition with the hole concentration P ≥ 3 × 1019 cm−3.

Asymmetric Al0.3Ga0.7As/GaAs/InGaAs heterostructures with a broadened waveguide produced by the method of MOCVD epitaxy are studied. It is established that the precision shift of the active region to one of the cladding layers ensures the generation of the chosen mode of high order in the transverse broadened waveguide. It is experimentally established that this shift brings about an increase in internal optical losses and a decrease in the internal quantum efficiency of stimulated emission. It is shown experimentally that the shift of the active region to the n-type cladding layer governs the sublinear form of the power-current characteristic for semiconductor lasers; in the case of a shift of the active region towards the p-type cladding layer, the laser diodes demonstrated a linear dependence of optical power on the pump current in the entire range of pump currents.

Charge-carrier heating and the carrier concentration dependence on electric current in quantum-well laser heterostructures have been studied under conditions of spontaneous and stimulated emission. Intersubband absorption in tunnel-coupled quantum wells has been investigated under charge-carrier heating by a lateral electric field and under high-power optical excitation.

Spectral and light-current characteristics of lasers based on the asymmetric separate-confinement heterostructures InGaAs/InGaAsAl/InP and InGaAs/GaAs/AlGaAs/GaAs were studied in the pulsed mode of lasing. It is shown that, at high levels of current pumping, the charge-carrier concentration in the active region of semiconductor lasers for the near-infrared optical region increases beyond the oscillation threshold; drastic saturation of the light-current characteristics is observed. Processes occurring in lasers as the charge-carrier concentration increases beyond the lasing threshold are studied theoretically. It is established that, at high pump levels, the rate of stimulated recombination decreases, the lifetime of charge carriers increases, and both the concentration of emitted photons and the quantum yield of stimulated radiation decrease. It is shown that variations in stimulated recombination, the decrease in the quantum efficiency, and saturation of the light-current characteristic in semiconductor lasers at high levels of current pumping are caused by the contribution of the nonradiative Auger recombination.

Spectral and emission-power characteristics of semiconductor lasers based on quantum-dimensional asymmetric heterostructures with separate confinement in a system of InGaAs/GaAs/AlGaAs alloys are studied in the case of high pump levels in the pulsed mode of lasing (200 A, 100 ns, and 10 kHz). It is shown that, in lasers with a quantum-dimensional active region containing one or two levels of dimensional quantization, the spectrum consists of one or two lasing bands. It is established that the condition for inverse population of the second electron level and two-band lasing are attained due to leveling-off of the rate of stimulated recombination from the first electron level and a high density of states for the second level. It is shown that, in lasers with double-band lasing spectrum, the total emission spectrum exceeds appreciably the emission power of a laser with a single electron level and a single spectral band.

Spectral and light-current characteristics of separate-confinement lasers that are based on InAl-GaAs/InP and InGaAsP/InP alloys and emit in the wavelength range of 1.5–1.8 μm are studied at high excitation levels (up to 80 kA/cm2) in pulse operation (100 ns, 10 kHz). It is shown that the peak intensity in the stimulated-emission spectrum saturates as the pump current is increased. Further increase in the emitted power is attained owing to the emission-spectrum broadening to shorter wavelengths, similar to lasers on the GaAs substrates (λ = 1.04 μm). It is established experimentally that the broadening of the stimulated-emission spectrum to shorter wavelengths is caused by an increase in the threshold current and by an increase in the charge-carrier concentration in the active region. This concentration increases by a factor of 6–7 beyond the lasing threshold and can be as high as 1019 cm−3 in pulse operation. It is shown that saturation of the light-current characteristics in pulse operation takes place in the InAlGaAs/InP and InGaAsP/InP lasers as the pump current is increased. It is shown experimentally that there is a correlation between saturation of the light-current characteristic and an increase in the threshold current in the active region. An increase in the charge-carrier concentration and gradual filling of the active region and waveguide layers with electrons are observed as the pump current is increased; stimulated emission from the waveguide is observed at high pump currents.

We suggested and experimentally confirmed the effective method of internal optical loss reduction by high order mode suppression in a separate confinement quantum well laser heterostructure with asymmetric ultra thick waveguide. Manufacturing of InGaAs/GaAs/AlGaAs laser heterostructure with a 1.7 microm-thick asymmetric waveguide allowed attaining super low value of internal optical loss alphai=0.34 cm-1 preserving high efficiency and fundamental transverse mode operation. Record-high 16 W continuous wave (CW) and 145 W pulse room temperature front facet output optical power and 74% wallplug efficiency were attained in 100-microm-aperture 1.06-microm-emitting laser diodes with 3 mm cavity length.

Generation of a difference-frequency wave by two electromagnetic waves propagating in a heterolaser is analyzed theoretically. Calculations are carried out for InGaAs/GaAs/AlGaAs heterostructures of design optimized to attain maximum lasing power. It is shown that phase matching between the primary waves and the difference-frequency wave may persist over a distance of ∼1 mm, comparable to the cavity length (2–3 mm), and the conversion coefficient can be as large as several percent.

It is shown that the reason why the maximum attainable optical power in semiconductor lasers is limited is the finite time of carrier energy relaxation via scattering by nonequilibrium optical phonons in the quantum-well active region. The power and spectral characteristics of semiconductor lasers are studied experimentally at high excitation levels (up to 100 kA/cm2) in pulsed lasing mode (100 ns, 10 kHz). As the drive current increases, the maximum intensity of stimulated emission tends to a constant value (“saturates”), and the emitted power increases owing to extension of the spectrum to shorter wavelengths. The intensity saturation is due to limitation of the rate of stimulated recombination, caused by a finite time of the electron energy relaxation via scattering by polar optical phonons. It is found that the broadening of the stimulated emission spectrum is related to an increase in carrier concentration in the active region, which enhances the escape of electrons into the waveguide layers. As the drive current increases, the carrier concentration in the waveguide reaches its threshold value and there appears an effective channel of current leakage from the active region. The experiment shows that the appearance of a band of waveguide lasing correlates with a sharp drop in the differential quantum efficiency of a semiconductor laser.

Asymmetric GaInAs/GaInAsP/AlGaAs heterostructures with the emission wavelength of 940 and 980 nm were grown by MOCVD. The composition of solid solution in the waveguide layer, Ga0.74In0.26As0.47P0.53, was chosen based on the calculations of the escape energy of electrons from the quantum well of the active region into the waveguide. Semiconductor lasers with the emission aperture of 100 μm were fabricated from these heterostructures. The CW output optical power of 12 W was achieved at room temperature. The internal optical loss was 0.6 and 0.3 cm−1 for 940 and 980 nm wavelengths, respectively.

Asymmetric separate-confinement laser heterostructures with ultrawide waveguides based on AlGaAs/GaAs/InGaAs solid solutions, with an emission wavelength of ∼1080 nm, are grown by MOCVD. The optical and electrical properties of mesa-stripe lasers with a stripe width of ∼100 μm are studied. Lasers based on asymmetric heterostructures with ultrawide (>1 μm) waveguides demonstrate lasing in the fundamental transverse mode with an internal optical loss of as low as 0.34 cm−1. In laser diodes with a cavity length of more than 3 mm, the thermal resistance is reduced to 2°C/W, and the characteristic temperature T 0= 10°C is obtained in the range 0–100°C. A record-breaking wallplug efficiency of 74% and an output optical power of 16 W are reached in CW mode. Mean-time-between-failures testing for 1000 h at 65°C with an operation power of 3–4 W results in the power decreasing by 3–7%.

Internal optical loss in separate-confinement laser heterostructures with an ultrawide (>1 smm) waveguide has been studied theoretically and experimentally. It is found that an asymmetric position of the active region in an ultrawide waveguide reduces the optical confinement factor for higher-order modes and raises the threshold electron density for these modes by 10–20%. It is shown that broadening the waveguide to above 1 µm results in a reduction of the internal optical loss only in asymmetric separate-confinement laser heterostructures. The calculated internal optical loss reaches ∼0.2 cm−1 (for λ≈1.08 µm) in an asymmetric waveguide 4 µm thick. The minimum internal optical loss has a fundamental limitation, which is determined by the loss from scattering on free carriers at the transparency carrier density in the active region. An internal optical loss of 0.34 cm−1 was attained in asymmetric separate-confinement laser heterostructures with an ultrawide (1.7 µm) waveguide, produced by MOCVD. Lasing in the fundamental transverse mode has been obtained owing to the significant difference in the threshold densities for the fundamental mode and higher-order modes. The record-breaking CW output optical power of 16 W and wallplug efficiency of 72% is obtained in 100-µm aperture lasers with a Fabry-Perot cavity length of ∼3 mm on the basis of the heterostructures produced.

Internal optical loss in high-power semiconductor lasers based on quantum-well separate-confinement heterostructures was studied. Calculations show that the major portion of the internal optical loss occurs in the active region and emitters. Making the laser waveguide thicker and the cavity longer reduces the internal optical loss. Two possible approaches to the design of laser heterostructures are considered, and optimal solutions are suggested. The difference in the internal optical loss between lasers on InP and those on GaAs substrates is attributed to the larger cross section of photon absorption by holes in InP. Good agreement between the calculated and experimental values of the internal optical loss in lasers on InP and GaAs substrates is obtained.

Separate-confinement InGaAsP/InP heterostructures with highly strained quantum wells are grown by metal-organic vapor-phase epitaxy (MOVPE). The properties of InGaAsP and InGaAs quantum wells are studied, and the influence of the heterostructure parameters on the lasing wavelength is analyzed. The grown structures are used for designing high-intensity multimode and single-mode mesa-stripe laser diodes operating in the range λ=1.7–1.8 µm. The maximum continuous-wave lasing power achieved at room temperature is 1.6 W and 150 mW for multimode and single-mode laser diodes, respectively. Single-mode lasing is retained up to 100 mW.

The possibility of achieving maximal optical output power in the single-mode lasing for mesa-stripe laser diodes fabricated on the basis of InGaAsP/InP quantum-well heterostructures with separate confinement have been studied both experimentally and theoretically. The basic condition for the single-mode lasing of laser diodes in a wide range of driving currents is shown to be the precise choice of the effective refractive index ΔnL discontinuity in the plane parallel to the p-n junction. A InGaAsP/InP separate confinement heterostructure with a step waveguide, with a threshold current density of 180 A/cm2 and an internal quantum efficiency of stimulated emission of 93–99%, has been manufactured via the MOCVD method. The optimization of the mesa-stripe diode design for the developed InGaAsP/InP heterostructure is carried out with the aim of achieving maximal optical output power in the case of single-mode lasing. An output power of 185 mW is attained in the laser diode with the mesa-stripe width W=4.5 μm (λ=1480 nm). The maximal continuous output power was as high as 300 mW. The full width at half-maximum (FWHM) of the lateral far-field pattern increased by 1° relative to the threshold value.

Single-mode and multimode quantum well (QW) laser diodes with emission wavelengths λ=1.0 and 1.58 µm, based on MOCVD-grown separate-confinement heterostructures, have been studied. An analysis of the threshold current density and optical gain is made on the basis of experimental dependences of the threshold current and differential quantum efficiency on the cavity length. The threshold current is decomposed into principal components in terms of model approximations taking into account the Auger recombination, ejection of electrons from QWs into waveguide layers, and lateral current spreading to passive regions of a mesa-stripe laser.

A MOCVD technology for growth of InGaAs/GaAs/InGaP laser heterostructures on a modified Epiquip VP-50-RP installation was developed. Mesa stripe laser diodes with threshold current density Jth=100–200 A/cm2, internal optical loss αi=1.3–1.7 cm−1, and internal quantum efficiency ηi=60–70% have been fabricated. A CW output optical power of 5 W has been obtained for a single 100-µm-wide aperture mesa stripe laser diode emitting at 1.03 µm. It is shown that use of AlGaAs waveguide layers, which increase the conduction band barrier offset, lowers the temperature sensitivity of laser heterostructures within the temperature range 10–80°C.

Epitaxially stacked tunnel-junction laser hetero structures were grown by hydride metalorganic vapor-phase epitaxy in the system of AlGaAs/GaAs/In GaAs alloys. Based on such structures, mesa stripe lasers with an aperture of 150 s- 7 m were fabricated. The possibility of controlling the lasing wavelength by varying the active region thickness in each tunnel-junction laser structure was demonstrated. Independent two-band lasing at wavelengths of 914 and 925 nm (the difference frequency is 2.3 THz) was achieved at a maximum optical radiation power of 20 W in each band of the epitaxially stacked tunnel-junction semiconductor laser.

Arrays of strained nanoscale InP islands in an In0.49Ga0.51P host on a GaAs(100) substrate and InAs islands in a In0.53Ga0.47As host on an InP(100) substrate are obtained by metalorganic vapor-phase epitaxy (MOVPE). Their structural and photoluminescence properties are investigated. It is shown that the nanoscale islands that are formed measure 80 nm (InP/InGaP) and 25–60 nm (InAs/InGaAs). The photoluminescence spectra of the nanoscale islands display bands in the wavelength ranges 0.66–0.72 and 1.66–1.91 µm at 77 K with maxima whose position does not vary as the effective thickness of InP and InAs increases. The radiation efficiency of the nanoscale InP islands is two orders of magnitude greater than the luminescence intensity of the InAs islands.

A microscopic quantum-mechanical analysis of the intervalence band absorption of radiation (IVA) with hole transition into the spin-orbit split-off band has been made. It was found that IVA can heavily influence the threshold characteristics and quantum efficiency of heterolasers based on InAs. A detailed study of the threshold characteristics as functions of temperature and heterostructure parameters has been analyzed taking into account IVA.

Control of spectral and spatial parameters of semiconductor lasers is a key element of their development and application. Surface integrated high-order distributed Bragg reflector (DBR) is the way to narrow diode laser spectrum preserving the conventional postgrowth process of laser diodes. On the other hand, high-order DBR has specific optical losses, which reduce optical output power. In this work we analyzed these specific optical losses and present design of laser resonator containing short front DBR, that allow to significantly reduce losses. With this approach, slope efficiency was greatly increased in contrast with conventional rear DBR laser diodes and 4 W optical output power with spectral width of less than 3 A was attained.

Separately bounded InGaAsP/InP laser heterostructures with two stressed quantum wells emitting at a wavelength of 1.8 μm were obtained by metalorganic vapor-phase epitaxy. The laser diodes with a strip width of 100 μm provide for an output radiation power of 1.2 W in the continuous operation mode at a temperature of 20°C. A minimum threshold current density was 320 A/cm2 and a differential quantum efficiency was ηd=28% for a Fabry-Perot resonator length of 1.4 mm. The internal optical losses in the laser heterostructure studied amounted to 5.6 cm−1.

Results of photoluminescence (PL) studies of self-organized nanoscale InP islands (quantum dots, QDs) in the In0.49Ga0.51P matrix, grown on a GaAs substrate by metalorganic vapor phase epitaxy (MOVPE), are presented. Dependences of the PL efficiency on temperature in the range 77–300 K and on excitation level at pumping power densities of 0.01–5 kW/cm2 have been obtained. The PL spectra are a superposition of emission peaks from QDs and the wetting layer. Their intensity ratio depends on the pumping power and temperature, and the emission wavelength varies in the range 0.65–0.73 µm. At 77 K and low excitation level, InP QDs exhibit high temperature stability of the emission wavelength and high quantum efficiency.

The results of gamma-ray burst observations made in the 10 keV - 8 MeV range with Konus-B instrument on Granat spacecraft are presented. 19 gamma-ray bursts and 60 solar flares have been measured altogether in 27 days at a sensitivity level of 5×10−8 - 5×10−7 erg/cm2. The fast spectral variability of bursts and the presence of features in their spectra in the form of absorption and emission lines are confirmed.

Power and spectral characteristics of Fabry-Perot semiconductor lasers based on at high excitation levels in pulsed lasing mode (200 A, 100 ns, 10 kHz) are investigated and double-band lasing is reached.